Refractory concrete and method of making



/-" p f ly a filler in the form of an aggr t to in either comminuted or granular form 1 Q REEERENc'E ""g i Patented June 11?;1950 i I UNITED PATENT OFFICE E.;Lobaush, South Plainfleld, N. 1., as- .signonto Universal Atlas Cement Company, a corporation ol'lndiana 1 T hl'o lh'rwving Application September 5, 1946, I

.SerialNo.695,033

13 Claims. (01.106-64) inventlonrelates .to an improved refrac- ,mix the components are present in the.'fo1lowry, more -particularly a refractory concrete-of 1ing amounts: a p

which an essential componentis calciumalumi- I Percent -natecem t. 7 2 r Topaz g '0.'437-91'.7 E ongthe objects of the-invention is the pro- Calcium aluminate cement. 4.37 -.-58.1 yision f an :improved refractory :composition efractory filler .-L0 91.2 yielding articles-such aszrefractory-structuresand dded free silica ".1... 3.5 42.5

shapes of improved strength at elevated :tem-

peratures, and of thememc ory b s l 10 which is generally known in the United States ingfmmsuchmmmsmmras-Lumnite cement. hsuch cemen-tiis also re- A further object of the invention resides lathe m m h alumina E i f method by which the improved refractory struc- EH2. or -l 'tures and shapes composed of such improved re- 4. am mined 3 as used above is fractory composition are made. tmwmafl paz-w as e-ensheatediin Such These and further objects of the invention will 5 mannerithat at qeast 1% my w 'ightc f itsmaxb be more readily apparent in the following demumioriglnal17 4%rfluorme remainstin the topaz.

The calclum'aluminatecement employedis one sc ip i n of preferred modifications of the The refractory filler is usuallyiinthe form rot vention. E a refractory aggregate -which may be fire ,cla

The present invention represents improvea d'fire-ibrlck,eXpanded'shale,ol ivir e, /nents in certain aspects of the teachings of 20 m d-a; c IE 1 111E,

Kocher Patent No. 2,416,700, issued March 4, 1947. a 'm ,mm rm'flfi It involves the discovery that improved properties 5 i. com matiomoflth'esem r a s 'dependin refractory concretes of the type referred to in 1 1113011 th -.use'.: .to -which :tlre refractoryr o that patent which contain as essential compccretedskto bezputy nents calcium alumlnate cement and topaz, and mle utuent mfrthe-mixsare supplie'dvth r may be secured by the additionto such mixes oi t allow them t b uniformly distributed free aianelradimlrdnsrorm- "within ithe'i" throughout the mix and consequently the resultlimits am the manner below specified. ing concrete. Those constituents which form the The refractory concrete 0! the present invenbond are preferably finely ground to facilitate tion, which may be employed for applications their reaction. The calcium aluminate cement, I such as those mentioned -in the'Kocher' -'patent, for example, may be of such fineness that pracismadefrom a mix, the constituents of which lie tically all particles will pass through a 100 mesh Jwithin'the same broad limits as those given by screen, and the topaz may be ground to any Kocher with the addition, however, of .finely diparticle size. It is preferred that the added silica vided free silica or silica flour, i. e.. quartz sand likewise be finely ground, for example, to a par-Z or tters flint, within the range of from 0.5 ticle size comparable to that of the cement,

i to 7 .U%"Ey weight of the total mix." The mix j although it is to be understood that such particle thus has the following composition, the compo- 40 size of the added silica is capable of considerable nents being given by per cent of the total weight variation. The refractory filler or aggregate may Y of th m1x; be of any desired particle size or range of particle Per cent size consistant with substantial uniformity of Topaz, raw or artl calcined 0.415-94.6 distribution through the resulting concrete. .The Calcium a uminate cement 4.15 -59.7 Particle size of the aggregate naturally will be .Refractory filler .0 -94.1 chosen with, the minimum sctionof the shape Added free silica... -015 17.0 or structure tobe'ma'de inview. v 'The'mix may conveniently bemadebymixing "It-is preferred forsom'e applications "that the the ca-lgjgmalgminate ement,"the topaz and the addedsilica liewithin the lim'its3.'5 to-12.5% "'adde'dfree silica indry condition to aunirorm by weight -01 "the "win 1h such preferred "color, therew ry aggregate being thoroughly wet down with my and then added to the mixture of the calcium aluminate, topaz and the added free silica. Suflicient water is added to the resulting mixture to render it workable, the amount added depending upon the manner in which the mix is to be subsequently handled in the formation of the concrete shape or structure. Thus, if the concrete is to be cast into a mold or form, particularly if the shape is intricate, the mix should be of puddling consistency. For simple shapes so cast, less water may be used, whereas if the mix is to be tamped or vibrated into place or molded under pressure, still less water may be used. It is obvious that sumcient water should be used in all cases to develop fully thehydraulic strength of the cement and that an excesspi water should be avoided. Besides above indicated, it is possible to deposit itin a mold or form or in any desired location, as for instance, in the applying of patches to existing structures, by charging the mix into a cement gun which pumps or otherwise forces it out through a discharge orifice.

After the mixture has been shaped or molded in any one of the'ways above described, it is dried and then heated. Usually for'bodies of large section, such as cast furnace walls, the practice follows approximately that employed in the drying and heating of newly constructed firebrick linings. The concrete may be air dried for a period of several days, after which the furnace is heated at temperatures which gradually in- 4 tion at room temperatures are shown by the results set out by the following Tables I and II giving the compressive strengths of 2 inch cubes made of mixtures containing the indicated per- 5 centages by weigh o @l fiu -Jyllsmfifii l llh tgga z, refractory aggrggate, and added free silica iii the rdrn afimca seat. In the making of such 2 inch test cubes the mix was made of a puddling consistency and poured into 2 inch cube holds. After treatment in a moist cabinet the cubes were dried at 230 F., flred for the indicated length of time at the indicated temperature, and were then allowed to cool. After cooling, each cube was subjected to a compressive strength test at room temperature by subjecting it to gradually increasing pressure until a point of failure of the cube was reached.

In Table 1, below, the mixes employed contained calcium aluminate cement to az, olivine and sil 9. our, w ereas e xes emp oyed in Table 11 contained calcium aluminate cement, topaz, crushed and silica flour. The calcium aluminate cement in all tests was ground to a size such that 14.7% remained on a 325 mesh sieve. The silica flour was ground to pass a 100 mesh sieve and the olivine and crushed flrebrick ranged in particle size from inch to dust. Each of the values given for each test in the following Tables I and It represents the average of tests so on three similar 2 inch cubes. The figures under each heading in the tables represent the pa; giant of such material in the total batch by weg crease up to operating temperature. TABLE I Small bodies and shapes, such as cast bricks, calcium aluminate cement-Olivine aaareaate tiles and slabs may be kept for a time, on the order of twenty-four hours in a high humidity- Compressive Stieilgtlfi constant temperature atmosphere, dried at a low per 0 ca Fir d 4 D s ttemperature, on the order of 230 F., and then Pffffli'ff 'Lf Flour 8 By a subjected to a high temperature approximating 1 8 F. 20008 F .that at which the shape will be used. for example, 2000 F. Percent Percent Percent Percent Concrete resulting from mixes made in 9.0- g 81.0 594 -overflred cordance with the present invention after hav- 3 1 351 {2 3 "'53" 3g ing been dried and heated as above possesses ing 5. 2 15. 1.0 966 1 80 creased strength, improved load bearing charac- 6 5,; 1 123 $18 $3 $2 teristics at elevated temperatures, and greater 5 gg- 2-; 2, ,2 abrasion resistance at elevated temperatures than 9 1 19 1 1 Q; i; 5; 523 similar concretes similarly treated, both made 10 21556 21108 without topaz and added silica, in accordance TABLE II I Calcium aluminate cement-crushed firebrick Comp. Strength lbs. per s silica iflnlzwlsiretd 4 days at Fired l .8 Cement Firebriek Topaz 1,1100 F. 2,ooq=r. 2,200F.

1 Prlca'nt Pageant Percent Percent 575 too 650 2 11.1 65. s 11. 1 1, 840 a, 221 a, 052 3 1e s m. o 16.8 2. 1 2, 104 a, 815 a, 425 4 1a. 4 83.1 16. 4 4. 1 2, 862 a, ass a, 992 11 11.1 65.8 129 4.2 2,044 3,058 2,963 o 11.1 65.8 8.55 8.55 2,681 3,654 4,112 a 12-: e1 1:1 tit til; 9 1018 I 6413 211 1618 11009 3,425 3,483

1 Electric furnace. Oil Fired Furnace.

with the prior art, and containing topaz but no added free siiica, in accordance with the teaching of the aforementioned Kocher patent. Such increased strength and load-bearing qualities of the concrete of the present inven- As seen from Table I, the addition of as small an amount as .5% by weight added free silica produced increased strengths in the cubes containing olivine as the aggregate fired at 2000 F., although the compressive strength of those fired *caeerme at'1600" I". remained about the same 'as those of test 2, containing no added free silica. with the increase in added silica to 1.0%, however, (Table I) marked increases in compressive strength of cubes fired at both 1600 and 2000 F. were obtained. Such increases continuing withcubes heated at both temperatures until the added free silica reached a value somewhat over 10.7%. Although the compressive strengths drop somewhat upon further addition of free silica, it has beenfound that the addition of as much as 17.0% free silica in olivine containing concretes gives concrete with compressive strengths markedly greater than those of similar concretes without the added free silica.

Similar results are obtained with concretes containing crushed flrebrick as the aggregate as is evident from the results set out in Table II. In such table the cubes of test 3 containing 2.1% added silica have noticeably increased compressive strengths over those of test 2 when fired at all three temperatures employed. Such improvement in compressive strength continues upon the addition of free silica in amounts somewhat greater than 16.4%, falling off slightly thereafter so that 17.0% added free silica may be placed as a practical upper limit in such mixes.

The reason why refractory concretes employing calcium aluminate cement and topaz with free silica added thereto in accordance with the present invention possess increased hot and cold strengths, load-bearing qualities and abrasion resistance, as compared to similar concretes without the added free silica is not fully understood. The theory which seems most fully to ac'cord'with the facts as now known is that the added silica which, of course, is free silica and is of the particle size such that it readily reacts with other components of the bond, is acted upon by the fluorine or HF released upon heating of the topaz arm a bad in which silica plays a large part, such silica being either silica per se in crystalline form or combined with alumina to form mullite in fine crystalline form. The improvement in strength of concretes by such addition of free silica appears most marked with aggregates containing little or no free silica.

Regardless of the correctness of such theory, it is possible to employ the present invention with concretes containing the added free silica but in which the topaz is not present in the mix, the concrete being subjected to the volatile products released by topaz when heated in proximity to the concrete. The various methods by which concrete may be subjected to such volatile rodugts of togaz have been set out in the a55ve denifle Koo er patent, and such methods may be practiced here in the same manner but with the exception that the mix shall contain addedfree silica within the defined limits. Thus the invention may be practiced, especially with smaller shapes, such as bricks, slabs, and tiles, by heating such shapes in a muflie furnace with a quantity of topaz in a crucible likewise placed in the muflie furnace. With larger shapes such as furnace walls and the like, the furnace or other part may be heated preparatory to being placed in service and thereafter subjected to the action of an atmosphere of volatile products of topaz. Such improvement in strength in refractory concrete containing calcium aluminate cement, refractory aggregate, and added free silica within the limits noted, may also be attained after the concrete has been in service by the diffusion into it at elevated temperatures of the volatile products given fi by topazwhen heated to at least 1400 F;, such heating of the body and the topaz adjacent thereto preferably being carried out at temperatures of at least 1600 F. v Whereas particular embodiments of the invention have been described above for purposes of illustration, it will be evident that numerous vari- 'ations of details are possible within the teaching of the invention. I desire to claim as new the following.- j

Iclaim:

1. A mix forforming refractory concrete comprising the following components by weight of themix: calcium aluminate cement from 4.15 to 59.7%, topaz containing from 1 to 17.4% by weight of fluorine from 0.415 to 94.6%, and silica flour from 0.5tc 17.0%. ff 2. A mix for forming refractory concrete comprlsingthe following components by weight of the mix: calcium'aluminate cement from 4.37 to 58.1%, topaz" containing from 1' to 17.4% by weight of fluorine from 0.437 to 91.7%, and silica flour from 3.5 to 12.5%.

3. A mix for forming refractory concrete comprising the following components by weight of the mix: calcium aluminate cement from 4.15 to 59.7%, topaz containing from 1 to 17.4% by weight of fluorine from 0.415 to 94.6%, refractory aggregate from 1 to 94.1%, and silica flour from 0.5 to 17.0%.

'4. A mix for forming refractory concrete comprising the following components by weight of the mix: calcium aluminate cement from 4.37 to 58.1%, topaz containing from 1 to 17.4% by weight of fluorine from 0.437 to 91.7%, refractory aggregate from 1 to 91.2%, and silica flour from 3.5 to 12.5%.

5. A refractory concrete formed from a mix comprising the following components b weight of the mix: calcium aluminate cement from 4.15 to 59.7%, topaz containing from 1 to 17.4% by weight of fluorine from 0.415 to 94.6%, and silica flour from 0.5 to 17.0%.

6. A refractory concrete formed from a mix comprising the following components by weight of the mix: calcium aluminate cement from 4.37 to 58.1%, topaz containing from 1 to 17.4% by weight of fluorine from 0.437 to 91.7%, and silica flour from 3.5 to 12.5%.

7. A refractory concrete formed from .a mix comprising the following components by weight of the mix: calcium aluminate cement from 4.15 to 59.7%, topaz containing from 1 to 17.4% by weight of fluorine from 0.415 to 94.6 refractory aggregate from 1 to 94.1%, and silica flour from 8. A refractory concrete formed from a mix comprising the following components by weight of the mix: calcium aluminate cement from 4.37 to 58.1%, topaz containing from 1 to 17.4% by weight of fluorine from 0.437 to 91.7%, refractory aggregate from 1 to 91.2%, and silica flour from. 3.5 to 12.5%.

9. A refractory concrete formed from a mix comprising the following components by weight of the mix: cement composed essentially of calcium aluminates from 4.15 to 59.7%, topaz containing'from 1 to 17.4% by weight of fluorine from 0.415 to 94.6%, refractory aggregate from 1 to 94.1%, and silica flour frbit: 0.5 to 17.0%.

10. The method of makingf'refractory concrete which comprises heating concrete resulting from a mix comprising the following components by weight of the mix: calcium aluminate cement from 4.15 to 59.7%, and silica flour from 0.5 to

EXAMINER 7- 17.0%, and subjecting it to contact with the fluorine given 005 by the heating of topaz at a temperature or 1600 F.

11. A method of making refractory concrete which comprises forming a mix comprising the following components by weight of the mix: calcium aluminate cement from 4.15 to 59.7%, refractory aggregate from 1 to 94.1%, and silica flour from 0.5 to 17.0%, hydrating the mix and forming therefrom a-concrete body, installing such body for service, and in the initial firing of the body subjecting it to contact with the fluorine given off by topaz when heated to 1400 F.

12. The method of treating a refractory concrete body formed from a mix of the following components by weight: calcium aluminate cement from 4.15 to 59.7%, refractory aggregate from ,1 to 94 .1%, and silica flour from 0.5 to 17.0%; which comprises heating said body and subjecting it to contact with the fluorine given off by topaz when heated to 1400 F.

n FER NcEs crrnn 4 The following references are of record in the flle of this patent:

' UNITED STATES PATENTS Number Name Date 2,416,700" Kocher Mar. 4. 1947 

1. A MIX FOR FORMING REFRACTORY CONCRETE COMPRISING THE FOLLOWING COMPONENTS BY WEIGHT OF THE MIX: CALCIUM ALUMINATE CEMENT FROM 4.15 TO 59.7%, TOPAZ CONTAINING FROM 1 TO 17.4% BY WEIGHT OF FLUORINE FROM 0.415 TO 94.6%, AND SILICA FLOUR FROM 0.5 TO 17.0%. 